1. Field of the Invention
This invention relates generally to plier-type tools and, more particularly, to a tool of this type which includes a pair of coacting wedges for automatically adjusting the tool proportionally to the size of a work piece engaged by its jaws whereby a thick or thin work piece can be consecutively engaged by the tool without the necessity of adjusting it for the size of the work piece.
2. Description of the Prior Art
This invention is an improvement of the self-adjusting locking tool described in U.S. Pat. No. 3,600,986, titled Self-Adjusting Locking Wrench, issued to Earl M. Baldwin, Jr., on Aug. 24, 1971, which, in turn, describes an improvement of the wrench described in U.S. Pat. No. Re 26,280, titled Self-Adjusting Plier-Type Toggle Locking Wrench, reissued to John L. Hostetter on Oct. 17, 1967. The Hostetter and Baldwin wrenches both utilize an elongated handle having a stationary jaw secured to the forward end, and a movable handle having a triangularly-shaped jaw pivotally connected to its forward end and partially received in a recess defined by the body portion of the first handle. A toggle link is pivotally connected at one end to the movable handle, with the other end extending rearwardly and into the recess in the stationary handle and pivotally connected to the forward end of a first of a pair of coacting wedges slidably disposed within the stationary handle. The forward end of the second wedge is connected by a spring to the rearward side of the movable jaw which exerts a constant forward pull on the second wedge. The inclined surfaces of the wedges are separated by a plate which is prevented from forward or rearward movement by integral laterally extending lugs which engage apertures formed in the side walls of the handle.
In operation, when the movable handle is moved toward the stationary handle, the toggle link moves the first wedge rearwardly to an extent proportional to the size of a work piece engaged between the jaws until the wedges jam against the separation or floater plate and against the surfaces of the recess in the stationary handle and are stopped from further movement.
While the Baldwin tool enjoyed acclaim by the trade and briefly found an important niche in the market, it disappeared and has been missing for many years, reportedly because of manufacturing difficulties. A complaint voiced by auto mechanics while the tool was available was that if accidentally dropped in oil the wedge system would sometimes fail, resulting in unwanted release of the tool from the work piece clamped between the jaws. The failure is believed to have been due to formation of a slippery film of oil between the wedge surfaces and the surfaces of the floater plate which reduced the friction between these relatively slidable elements to a degree that even if the wedges are jammed against the floater plate and the surfaces of the recess in the stationary handle, the clamping force on the work piece transferred through the toggle link to the locking unit would cause one or both of the wedges to move enough to release them.
Accordingly, there exists a need for, and it is a primary object of this invention to provide, a self-adjusting plier-type locking tool having an interconnectable self-adjusting and locking wedge system which is not prone to failure if accidently immersed in oil.
Another object is to provide a self-adjusting tool having a pressure adjustment screw disposed to be easily accessible and which can be provided at minimal expense.
The self-adjusting locking tool of this invention has a pair of plier-like handles, the first of which has a stationary jaw, and the second of which has a movable jaw pivotally connected thereto and also to the first handle, and a toggle link pivotally connected at one end to the movable handle and pivotally connected at the other end to a first of a pair of coacting wedges slidably disposed within an enclosure in the stationary handle. The forward end of the second wedge is urged forwardly by a compression spring which surrounds a shaft which threadably engages the wedge and is disposed between the rear end of the wedge and the rear wall of the enclosure. The forward end of this shaft projects from the forward end of the wedge into engagement with a rearwardly facing shoulder formed on the toggle link.
The floating wedge is separated from the hinged wedge by a floater plate having parallel planar upper and lower surfaces, and means are provided for magnetically attracting the wedges into such close adjacency with the floater plate as to wipe away any oil that may be present and thus prevent slippery film formation therebetween, while still allowing the wedges and floater plate to slide relative to one another.